The present invention relates to a stepping motor.
In a related stepping motor having a stator constituted to be arranged with magnetic pole teeth at a surrounding of a rotor and to be wound with a coil around an axial line direction of the rotor for exciting the magnetic pole teeth, detent torque is generated between the rotor of a permanent magnet and the stator.
Further, it is known that detent torque is similarly generated in a motor of a so-called hybrid type having a motor stator constituted by providing a plurality of side magnetic poles and wound with a plurality of phases of an excitation winding as it a stepping motor described in Japanese patent publication Sho. 64-30672A or Japanese Utility Model Examined Publication Hei. 7-33583B.
The detent torque is generated also when current is not conducted to the coil and therefore, there is achieved an advantage of capable of self-holding a rotor.
Further, in Japanese Utility Model Publication Hei. 5-6718A, there is described a roller having a permanent magnet magnetized in a thickness direction and a pair of inductor plates interposing the magnet from both ends in the thickness direction.
However, when, for example, microstep drive is carried out by using a stepping motor generating such a detent torque, there is a case in which it is difficult to position the rotor at high speed by influence of the detent torque, which constitutes one factor of hampering high speed response of a stepping motor. On the other hand, there is also present a request of small-sized formation for the stepping motor.